diff --git a/bin/migrations/m20210308.ml b/bin/migrations/m20210308.ml
index b712b0d..bc24cbc 100644
--- a/bin/migrations/m20210308.ml
+++ b/bin/migrations/m20210308.ml
@@ -3,7 +3,7 @@ module Rep = Builder_db.Rep
 let broken_builds =
   Caqti_request.collect ~oneshot:true
     Caqti_type.unit
-    (Caqti_type.tup3 Rep.id Rep.uuid Caqti_type.string)
+    (Caqti_type.tup3 (Rep.id `build) Rep.uuid Caqti_type.string)
     {| SELECT b.id, b.uuid, job.name FROM build b, job
        WHERE result_kind = 0 AND result_code = 0 AND main_binary IS NOT NULL AND job.id = b.job AND
          (SELECT COUNT( * ) FROM build_artifact a
@@ -15,7 +15,7 @@ let fixup _datadir (module Db : Caqti_blocking.CONNECTION) =
   Grej.check_version ~user_version:3L (module Db) >>= fun () ->
   Db.rev_collect_list broken_builds () >>= fun broken_builds ->
   Grej.list_iter_result
-    (fun ((build, uuid, job_name) : Rep.id * Uuidm.t * string) ->
+    (fun ((build, uuid, job_name) : [`build] Rep.id * Uuidm.t * string) ->
        Format.printf "Removing job %a.\nPlease clean up data files in /var/db/builder-web/%s/%a\n"
          Uuidm.pp uuid job_name Uuidm.pp uuid;
        Db.exec Builder_db.Build.remove build)
diff --git a/bin/migrations/m20210531.ml b/bin/migrations/m20210531.ml
index da5255c..6c334c3 100644
--- a/bin/migrations/m20210531.ml
+++ b/bin/migrations/m20210531.ml
@@ -7,12 +7,12 @@ let rollback_doc = "add datadir prefix to build_artifact.localpath"
 let build_artifacts =
   Caqti_request.collect ~oneshot:true
     Caqti_type.unit
-    Caqti_type.(tup2 Builder_db.Rep.id Builder_db.Rep.fpath)
+    Caqti_type.(tup2 Builder_db.Rep.untyped_id Builder_db.Rep.fpath)
     "SELECT id, localpath FROM build_artifact"
 
 let build_artifact_update_localpath =
   Caqti_request.exec ~oneshot:true
-    Caqti_type.(tup2 Builder_db.Rep.id Builder_db.Rep.fpath)
+    Caqti_type.(tup2 Builder_db.Rep.untyped_id Builder_db.Rep.fpath)
     "UPDATE build_artifact SET localpath = ?2 WHERE id = ?1"
 
 (* We are not migrating build_file because it is unused *)
diff --git a/bin/migrations/m20210602.ml b/bin/migrations/m20210602.ml
index f5689e6..c2c0be1 100644
--- a/bin/migrations/m20210602.ml
+++ b/bin/migrations/m20210602.ml
@@ -55,18 +55,18 @@ let old_build =
 let collect_old_build =
   Caqti_request.collect ~oneshot:true
     Caqti_type.unit
-    Caqti_type.(tup3 Builder_db.Rep.id
+    Caqti_type.(tup3 Builder_db.Rep.untyped_id
       (tup3 (tup4 string int64 int64 int64) (tup4 int64 int (option int) (option string)) (tup3 octets string (option string)))
-      Builder_db.Rep.id)
+      Builder_db.Rep.untyped_id)
     {| SELECT id, uuid, start_d, start_ps, finish_d, finish_ps, result_kind, result_code, result_msg,
               console, script, main_binary, job
        FROM build |}
 
 let insert_new_build =
   Caqti_request.exec ~oneshot:true
-    Caqti_type.(tup3 Builder_db.Rep.id
-      (tup3 (tup4 string int64 int64 int64) (tup4 int64 int (option int) (option string)) (tup3 octets string (option Builder_db.Rep.id)))
-      Builder_db.Rep.id)
+    Caqti_type.(tup3 Builder_db.Rep.untyped_id
+      (tup3 (tup4 string int64 int64 int64) (tup4 int64 int (option int) (option string)) (tup3 octets string (option Builder_db.Rep.untyped_id)))
+      Builder_db.Rep.untyped_id)
     {| INSERT INTO new_build (id, uuid, start_d, start_ps, finish_d, finish_ps, result_kind,
                               result_code, result_msg, console, script, main_binary, job)
        VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?) |}
@@ -83,31 +83,31 @@ let rename_build =
 
 let find_main_artifact_id =
   Caqti_request.find ~oneshot:true
-    Caqti_type.(tup2 Builder_db.Rep.id string)
-    Builder_db.Rep.id
+    Caqti_type.(tup2 Builder_db.Rep.untyped_id string)
+    Builder_db.Rep.untyped_id
     "SELECT id FROM build_artifact WHERE build = ?1 AND filepath = ?2"
 
 let find_main_artifact_filepath =
   Caqti_request.find ~oneshot:true
-    Builder_db.Rep.id
+    Builder_db.Rep.untyped_id
     Caqti_type.string
     "SELECT filepath FROM build_artifact WHERE id = ?"
 
 let collect_new_build =
   Caqti_request.collect ~oneshot:true
     Caqti_type.unit
-    Caqti_type.(tup3 Builder_db.Rep.id
-      (tup3 (tup4 string int64 int64 int64) (tup4 int64 int (option int) (option string)) (tup3 octets string (option Builder_db.Rep.id)))
-      Builder_db.Rep.id)
+    Caqti_type.(tup3 Builder_db.Rep.untyped_id
+      (tup3 (tup4 string int64 int64 int64) (tup4 int64 int (option int) (option string)) (tup3 octets string (option Builder_db.Rep.untyped_id)))
+      Builder_db.Rep.untyped_id)
     {| SELECT id, uuid, start_d, start_ps, finish_d, finish_ps, result_kind, result_code, result_msg,
               console, script, main_binary, job
        FROM build |}
   
 let insert_old_build =
   Caqti_request.exec ~oneshot:true
-    Caqti_type.(tup3 Builder_db.Rep.id
+    Caqti_type.(tup3 Builder_db.Rep.untyped_id
       (tup3 (tup4 string int64 int64 int64) (tup4 int64 int (option int) (option string)) (tup3 octets string (option string)))
-      Builder_db.Rep.id)
+      Builder_db.Rep.untyped_id)
     {| INSERT INTO new_build (id, uuid, start_d, start_ps, finish_d, finish_ps, result_kind,
                               result_code, result_msg, console, script, main_binary, job)
        VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?) |}
diff --git a/bin/migrations/m20210609.ml b/bin/migrations/m20210609.ml
index 594231b..0fcfd8d 100644
--- a/bin/migrations/m20210609.ml
+++ b/bin/migrations/m20210609.ml
@@ -68,7 +68,7 @@ let old_build =
 
 let insert_from_old_build =
   Caqti_request.exec ~oneshot:true
-    Builder_db.Rep.id
+    (Builder_db.Rep.id (`user : [`user]))
     {| INSERT INTO new_build (id, uuid, start_d, start_ps, finish_d, finish_ps,
                               result_kind, result_code, result_msg, console,
                               script, main_binary, job, user)
diff --git a/bin/migrations/m20210629.ml b/bin/migrations/m20210629.ml
index 695ae07..110e1d0 100644
--- a/bin/migrations/m20210629.ml
+++ b/bin/migrations/m20210629.ml
@@ -30,13 +30,13 @@ let job_tag =
 let jobs =
   Caqti_request.collect
     Caqti_type.unit
-    Builder_db.Rep.id
+    Builder_db.Rep.untyped_id
     "SELECT id FROM job"
 
 let latest_successful_build =
   Caqti_request.find_opt
-    Builder_db.Rep.id
-    Builder_db.Rep.id
+    Builder_db.Rep.untyped_id
+    Builder_db.Rep.untyped_id
     {| SELECT b.id
        FROM build b
        WHERE b.job = ? AND b.result_kind = 0 AND b.result_code = 0
@@ -46,7 +46,7 @@ let latest_successful_build =
 
 let build_artifacts =
   Caqti_request.collect
-    Builder_db.Rep.id
+    Builder_db.Rep.untyped_id
     Caqti_type.(tup2 Builder_db.Rep.fpath Builder_db.Rep.fpath)
     {| SELECT a.filepath, a.localpath
        FROM build_artifact a
@@ -115,13 +115,13 @@ let insert_tag =
 
 let insert_job_tag =
    Caqti_request.exec
-     Caqti_type.(tup3 Builder_db.Rep.id string Builder_db.Rep.id)
+     Caqti_type.(tup3 Builder_db.Rep.untyped_id string Builder_db.Rep.untyped_id)
      "INSERT INTO job_tag (tag, value, job) VALUES (?, ?, ?)"
 
 let find_tag =
    Caqti_request.find
      Caqti_type.string
-     Builder_db.Rep.id
+     Builder_db.Rep.untyped_id
      "SELECT id FROM tag where tag = ?"
 
 open Rresult.R.Infix
diff --git a/bin/migrations/m20210630.ml b/bin/migrations/m20210630.ml
index f60f58f..cf16dd6 100644
--- a/bin/migrations/m20210630.ml
+++ b/bin/migrations/m20210630.ml
@@ -6,13 +6,13 @@ let rollback_doc = "remove readme.md tag"
 let jobs =
   Caqti_request.collect
     Caqti_type.unit
-    Builder_db.Rep.id
+    Builder_db.Rep.untyped_id
     "SELECT id FROM job"
 
 let latest_successful_build =
   Caqti_request.find_opt
-    Builder_db.Rep.id
-    Builder_db.Rep.id
+    Builder_db.Rep.untyped_id
+    Builder_db.Rep.untyped_id
     {| SELECT b.id
        FROM build b
        WHERE b.job = ? AND b.result_kind = 0 AND b.result_code = 0
@@ -22,7 +22,7 @@ let latest_successful_build =
 
 let build_artifacts =
   Caqti_request.collect
-    Builder_db.Rep.id
+    Builder_db.Rep.untyped_id
     Caqti_type.(tup2 Builder_db.Rep.fpath Builder_db.Rep.fpath)
     {| SELECT a.filepath, a.localpath
        FROM build_artifact a
@@ -36,23 +36,23 @@ let insert_tag =
 
 let insert_job_tag =
    Caqti_request.exec
-     Caqti_type.(tup3 Builder_db.Rep.id string Builder_db.Rep.id)
+     Caqti_type.(tup3 Builder_db.Rep.untyped_id string Builder_db.Rep.untyped_id)
      "INSERT INTO job_tag (tag, value, job) VALUES (?, ?, ?)"
 
 let find_tag =
    Caqti_request.find
      Caqti_type.string
-     Builder_db.Rep.id
+     Builder_db.Rep.untyped_id
      "SELECT id FROM tag where tag = ?"
 
 let remove_job_tag =
    Caqti_request.exec
-     Builder_db.Rep.id
+     Builder_db.Rep.untyped_id
      "DELETE FROM job_tag where tag = ?"
 
 let remove_tag =
    Caqti_request.exec
-     Builder_db.Rep.id
+     Builder_db.Rep.untyped_id
      "DELETE FROM tag where id = ?"
 
 open Rresult.R.Infix
diff --git a/db/builder_db.ml b/db/builder_db.ml
index 180369c..257e165 100644
--- a/db/builder_db.ml
+++ b/db/builder_db.ml
@@ -6,7 +6,7 @@ let application_id = 1234839235l
 (* Please update this when making changes! *)
 let current_version = 11L
 
-type id = Rep.id
+type 'a id = 'a Rep.id
 
 type file = Rep.file = {
   filepath : Fpath.t;
@@ -15,12 +15,7 @@ type file = Rep.file = {
   size : int;
 }
 
-let last_insert_rowid =
-  Caqti_request.find
-    Caqti_type.unit
-    id
-    "SELECT last_insert_rowid()"
-
+let last_insert_rowid = Rep.last_insert_rowid
 
 let get_application_id =
   Caqti_request.find
@@ -61,26 +56,26 @@ module Job = struct
 
   let get =
     Caqti_request.find
-      id
+      (id `job)
       Caqti_type.string
       "SELECT name FROM job WHERE id = ?"
 
   let get_id_by_name =
     Caqti_request.find_opt
       Caqti_type.string
-      id
+      (id `job)
       "SELECT id FROM job WHERE name = ?"
 
   let get_all =
     Caqti_request.collect
       Caqti_type.unit
-      Caqti_type.(tup2 id string)
+      Caqti_type.(tup2 (id `job) string)
       "SELECT id, name FROM job ORDER BY name ASC"
 
   let get_all_with_section_synopsis =
     Caqti_request.collect
       Caqti_type.unit
-      Caqti_type.(tup4 id string (option string) (option string))
+      Caqti_type.(tup4 (id `job) string (option string) (option string))
       {| SELECT j.id, j.name, section.value, synopsis.value
          FROM job j, tag section_tag, tag synopsis_tag
          LEFT JOIN job_tag section ON section.job = j.id AND section.tag = section_tag.id
@@ -96,7 +91,7 @@ module Job = struct
 
   let remove =
     Caqti_request.exec
-      id
+      (id `job)
       "DELETE FROM job WHERE id = ?"
 end
 
@@ -117,14 +112,14 @@ module Tag = struct
 
   let get =
     Caqti_request.find
-      id
+      (id `tag)
       Caqti_type.string
       "SELECT tag FROM tag WHERE id = ?"
 
   let get_id_by_name =
     Caqti_request.find
       Caqti_type.string
-      id
+      (id `tag)
       "SELECT id FROM tag WHERE tag = ?"
 
   let try_add =
@@ -156,17 +151,17 @@ module Job_tag = struct
 
   let add =
     Caqti_request.exec
-      Caqti_type.(tup3 id string id)
+      Caqti_type.(tup3 (id `tag) string (id `job))
       "INSERT INTO job_tag (tag, value, job) VALUES (?1, ?2, ?3)"
 
   let update =
     Caqti_request.exec
-      Caqti_type.(tup3 id string id)
+      Caqti_type.(tup3 (id `tag) string (id `job))
       "UPDATE job_tag SET value = ?2 WHERE tag = ?1 AND job = ?3"
 
   let get_value =
     Caqti_request.find_opt
-      Caqti_type.(tup2 id id)
+      Caqti_type.(tup2 (id `tag) (id `job))
       Caqti_type.string
       "SELECT value FROM job_tag WHERE tag = ? AND job = ?"
 end
@@ -195,8 +190,8 @@ module Build_artifact = struct
 
   let get_by_build =
     Caqti_request.find
-      (Caqti_type.tup2 id fpath)
-      (Caqti_type.tup2 id file)
+      (Caqti_type.tup2 (id `build) fpath)
+      (Caqti_type.tup2 (id `build_artifact) file)
       {| SELECT id, filepath, localpath, sha256, size
          FROM build_artifact
          WHERE build = ? AND filepath = ?
@@ -205,7 +200,7 @@ module Build_artifact = struct
   let get_by_build_uuid =
     Caqti_request.find_opt
       (Caqti_type.tup2 uuid fpath)
-      (Caqti_type.tup2 id file)
+      (Caqti_type.tup2 (id `build_artifact) file)
       {| SELECT build_artifact.id, build_artifact.filepath,
            build_artifact.localpath, build_artifact.sha256, build_artifact.size
          FROM build_artifact
@@ -215,26 +210,26 @@ module Build_artifact = struct
 
   let get_all_by_build =
     Caqti_request.collect
-      id
+      (id `build)
       Caqti_type.(tup2
-                    id
+                    (id `build_artifact)
                     file)
       "SELECT id, filepath, localpath, sha256, size FROM build_artifact WHERE build = ?"
 
   let add =
     Caqti_request.exec
-      Caqti_type.(tup2 file id)
+      Caqti_type.(tup2 file (id `build))
       "INSERT INTO build_artifact (filepath, localpath, sha256, size, build)
         VALUES (?, ?, ?, ?, ?)"
 
   let remove_by_build =
     Caqti_request.exec
-      id
+      (id `build)
       "DELETE FROM build_artifact WHERE build = ?"
 
   let remove =
     Caqti_request.exec
-      id
+      (id `build_artifact)
       "DELETE FROM build_artifact WHERE id = ?"
 end
 
@@ -246,9 +241,9 @@ module Build = struct
     result : Builder.execution_result;
     console : (int * string) list;
     script : string;
-    main_binary : id option;
-    user_id : id;
-    job_id : id;
+    main_binary : [`build_artifact] id option;
+    user_id : [`user] id;
+    job_id : [`job] id;
   }
 
   let t =
@@ -264,9 +259,9 @@ module Build = struct
                           console)
                        (tup2
                           string
-                          (option Rep.id)))
-                    id
-                    id)
+                          (option (Rep.id `build_artifact))))
+                    (id `user)
+                    (id `job))
     in
     let encode { uuid; start; finish; result; console; script; main_binary; user_id; job_id } =
       Ok ((uuid, (start, finish), (result, console), (script, main_binary)), user_id, job_id)
@@ -282,9 +277,9 @@ module Build = struct
       start : Ptime.t;
       finish : Ptime.t;
       result : Builder.execution_result;
-      main_binary : id option;
-      user_id : id;
-      job_id : id;
+      main_binary : [`build_artifact] id option;
+      user_id : [`user] id;
+      job_id : [`job] id;
     }
 
     let t =
@@ -296,9 +291,9 @@ module Build = struct
                           Rep.ptime
                           Rep.ptime)
                        execution_result
-                       (option Rep.id))
-                     id
-                     id)
+                       (option (Rep.id `build_artifact)))
+                     (id `user)
+                     (id `job))
       in
       let encode { uuid; start; finish; result; main_binary; user_id; job_id } =
         Ok ((uuid, (start, finish), result, main_binary), user_id, job_id)
@@ -341,7 +336,7 @@ module Build = struct
 
   let get_opt =
     Caqti_request.find_opt
-      Caqti_type.int64
+      (id `build)
       t
       {| SELECT uuid, start_d, start_ps, finish_d, finish_ps,
                 result_kind, result_code, result_msg,
@@ -353,7 +348,7 @@ module Build = struct
   let get_by_uuid =
     Caqti_request.find_opt
       Rep.uuid
-      (Caqti_type.tup2 id t)
+      (Caqti_type.tup2 (id `build) t)
       {| SELECT id, uuid, start_d, start_ps, finish_d, finish_ps,
                   result_kind, result_code, result_msg,
                   console, script, main_binary, user, job
@@ -363,8 +358,8 @@ module Build = struct
 
   let get_all =
     Caqti_request.collect
-      Caqti_type.int64
-      (Caqti_type.tup2 id t)
+      (id `job)
+      (Caqti_type.tup2 (id `build) t)
       {| SELECT id, uuid, start_d, start_ps, finish_d, finish_ps,
                   result_kind, result_code, result_msg, console,
                   script, main_binary, user, job
@@ -375,9 +370,9 @@ module Build = struct
 
   let get_all_meta =
     Caqti_request.collect
-      Caqti_type.int64
+      (id `job)
       (Caqti_type.tup3
-         id Meta.t file_opt)
+         (id `build) Meta.t file_opt)
       {| SELECT build.id, build.uuid,
                 build.start_d, build.start_ps, build.finish_d, build.finish_ps,
                 build.result_kind, build.result_code, build.result_msg,
@@ -392,9 +387,9 @@ module Build = struct
 
   let get_latest =
     Caqti_request.find_opt
-      id
+      (id `job)
       Caqti_type.(tup3
-                   id
+                   (id `build)
                    Meta.t
                    file_opt)
       {| SELECT b.id,
@@ -412,8 +407,8 @@ module Build = struct
 
   let get_latest_uuid =
     Caqti_request.find_opt
-      id
-      Caqti_type.(tup2 id Rep.uuid)
+      (id `job)
+      Caqti_type.(tup2 (id `build) Rep.uuid)
       {| SELECT b.id, b.uuid
          FROM build b
          WHERE b.job = ?
@@ -423,7 +418,7 @@ module Build = struct
 
   let get_latest_successful_uuid =
     Caqti_request.find_opt
-      id
+      (id `job)
       Rep.uuid
       {| SELECT b.uuid
          FROM build b
@@ -434,8 +429,8 @@ module Build = struct
 
   let get_previous_successful =
     Caqti_request.find_opt
-      id
-      Caqti_type.(tup2 id Meta.t)
+      (id `build)
+      Caqti_type.(tup2 (id `build) Meta.t)
       {| SELECT b.id,
            b.uuid, b.start_d, b.start_ps, b.finish_d, b.finish_ps,
            b.result_kind, b.result_code, b.result_msg,
@@ -478,12 +473,12 @@ module Build = struct
 
   let set_main_binary =
     Caqti_request.exec
-      (Caqti_type.tup2 id id)
+      (Caqti_type.tup2 (id `build) (id `build_artifact))
       "UPDATE build SET main_binary = ?2 WHERE id = ?1"
 
   let remove =
     Caqti_request.exec
-      id
+      (id `build)
       "DELETE FROM build WHERE id = ?"
 end
 
@@ -511,7 +506,7 @@ module User = struct
   let get_user =
     Caqti_request.find_opt
       Caqti_type.string
-      (Caqti_type.tup2 id user_info)
+      (Caqti_type.tup2 (id `user) user_info)
       {| SELECT id, username, password_hash, password_salt,
            scrypt_n, scrypt_r, scrypt_p, restricted
          FROM user
@@ -534,7 +529,7 @@ module User = struct
 
   let remove =
     Caqti_request.exec
-      id
+      (id `user)
       "DELETE FROM user WHERE id = ?"
 
   let remove_user =
@@ -578,18 +573,18 @@ module Access_list = struct
 
   let get =
     Caqti_request.find
-      Caqti_type.(tup2 Rep.id Rep.id)
-      Rep.id
+      Caqti_type.(tup2 (id `user) (id `job))
+      (id `access_list)
       "SELECT id FROM access_list WHERE user = ? AND job = ?"
 
   let add =
     Caqti_request.exec
-      Caqti_type.(tup2 Rep.id Rep.id)
+      Caqti_type.(tup2 (id `user) (id `job))
       "INSERT INTO access_list (user, job) VALUES (?, ?)"
 
   let remove =
     Caqti_request.exec
-      Caqti_type.(tup2 Rep.id Rep.id)
+      Caqti_type.(tup2 (id `user) (id `job))
       "DELETE FROM access_list WHERE user = ? AND job = ?"
 
   let remove_all_by_username =
diff --git a/db/builder_db.mli b/db/builder_db.mli
index 70973e0..d893d48 100644
--- a/db/builder_db.mli
+++ b/db/builder_db.mli
@@ -1,5 +1,6 @@
 module Rep : sig
-  type id
+  type untyped_id
+  type 'a id
   type file = {
     filepath : Fpath.t;
     localpath : Fpath.t;
@@ -7,7 +8,8 @@ module Rep : sig
     size : int;
   }
 
-  val id : id Caqti_type.t
+  val untyped_id : untyped_id Caqti_type.t
+  val id : 'a -> 'a id Caqti_type.t
   val uuid : Uuidm.t Caqti_type.t
   val ptime : Ptime.t Caqti_type.t
   val fpath : Fpath.t Caqti_type.t
@@ -16,7 +18,7 @@ module Rep : sig
   val execution_result : Builder.execution_result Caqti_type.t
   val console : (int * string) list Caqti_type.t
 end
-type id = Rep.id
+type 'a id = 'a Rep.id
 
 type file = Rep.file = {
   filepath : Fpath.t;
@@ -42,7 +44,7 @@ val set_current_version :
   (unit, unit, [< `Many | `One | `Zero > `Zero ]) Caqti_request.t
 
 val last_insert_rowid :
-  (unit, id, [< `Many | `One | `Zero > `One ]) Caqti_request.t
+  (unit, 'a id, [< `Many | `One | `Zero > `One ]) Caqti_request.t
 
 module Job : sig
   val migrate :
@@ -51,18 +53,18 @@ module Job : sig
     (unit, unit, [< `Many | `One | `Zero > `Zero ]) Caqti_request.t
 
   val get :
-    (id, string, [< `Many | `One | `Zero > `One ])
+    ([`job] id, string, [< `Many | `One | `Zero > `One ])
       Caqti_request.t
   val get_id_by_name :
-    (string, id, [< `Many | `One | `Zero > `One `Zero ]) Caqti_request.t
+    (string, [`job] id, [< `Many | `One | `Zero > `One `Zero ]) Caqti_request.t
   val get_all :
-    (unit, id * string, [ `Many | `One | `Zero ]) Caqti_request.t
+    (unit, [`job] id * string, [ `Many | `One | `Zero ]) Caqti_request.t
   val get_all_with_section_synopsis :
-    (unit, id * string * string option * string option, [ `Many | `One | `Zero ]) Caqti_request.t
+    (unit, [`job] id * string * string option * string option, [ `Many | `One | `Zero ]) Caqti_request.t
   val try_add :
     (string, unit, [< `Many | `One | `Zero > `Zero ]) Caqti_request.t
   val remove :
-    (id, unit, [< `Many | `One | `Zero > `Zero ]) Caqti_request.t
+    ([`job] id, unit, [< `Many | `One | `Zero > `Zero ]) Caqti_request.t
 end
 
 module Tag : sig
@@ -71,9 +73,9 @@ module Tag : sig
   val rollback :
     (unit, unit, [< `Many | `One | `Zero > `Zero ]) Caqti_request.t
   val get :
-    (id, string, [< `Many | `One | `Zero > `One ]) Caqti_request.t
+    ([`tag] id, string, [< `Many | `One | `Zero > `One ]) Caqti_request.t
   val get_id_by_name :
-    (string, id, [< `Many | `One | `Zero > `One ]) Caqti_request.t
+    (string, [`tag] id, [< `Many | `One | `Zero > `One ]) Caqti_request.t
   val try_add :
     (string, unit, [< `Many | `One | `Zero > `Zero ]) Caqti_request.t
 end
@@ -84,11 +86,11 @@ module Job_tag : sig
   val rollback :
     (unit, unit, [< `Many | `One | `Zero > `Zero ]) Caqti_request.t
   val add :
-    (id * string * id, unit, [< `Many | `One | `Zero > `Zero ]) Caqti_request.t
+    ([`tag] id * string * [`job] id, unit, [< `Many | `One | `Zero > `Zero ]) Caqti_request.t
   val update :
-    (id * string * id, unit, [< `Many | `One | `Zero > `Zero ]) Caqti_request.t
+    ([`tag] id * string * [`job] id, unit, [< `Many | `One | `Zero > `Zero ]) Caqti_request.t
   val get_value :
-    (id * id, string, [< `Many | `One | `Zero > `Zero `One ]) Caqti_request.t
+    ([`tag] id * [`job] id, string, [< `Many | `One | `Zero > `Zero `One ]) Caqti_request.t
 end
 
 module Build_artifact : sig
@@ -98,21 +100,21 @@ module Build_artifact : sig
     (unit, unit, [< `Many | `One | `Zero > `Zero ]) Caqti_request.t
 
   val get_by_build :
-    (id * Fpath.t, id * file,
+    ([`build] id * Fpath.t, [`build_artifact] id * file,
      [< `Many | `One | `Zero > `One ]) Caqti_request.t
 
   val get_by_build_uuid :
-    (Uuidm.t * Fpath.t, id * file,
+    (Uuidm.t * Fpath.t, [`build_artifact] id * file,
      [< `Many | `One | `Zero > `One `Zero ])
       Caqti_request.t
   val get_all_by_build :
-    (id, id * file, [ `Many | `One | `Zero ]) Caqti_request.t
+    ([`build] id, [`build_artifact] id * file, [ `Many | `One | `Zero ]) Caqti_request.t
   val add :
-    (file * id, unit, [< `Many | `One | `Zero > `Zero ]) Caqti_request.t
+    (file * [`build] id, unit, [< `Many | `One | `Zero > `Zero ]) Caqti_request.t
   val remove_by_build :
-    (id, unit, [< `Many | `One | `Zero > `Zero ]) Caqti_request.t
+    ([`build] id, unit, [< `Many | `One | `Zero > `Zero ]) Caqti_request.t
   val remove :
-    (id, unit, [< `Many | `One | `Zero > `Zero ]) Caqti_request.t
+    ([`build_artifact] id, unit, [< `Many | `One | `Zero > `Zero ]) Caqti_request.t
 end
 
 module Build :
@@ -124,9 +126,9 @@ sig
     result : Builder.execution_result;
     console : (int * string) list;
     script : string;
-    main_binary : id option;
-    user_id : id;
-    job_id : id;
+    main_binary : [`build_artifact] id option;
+    user_id : [`user] id;
+    job_id : [`job] id;
   }
   module Meta :
   sig
@@ -135,9 +137,9 @@ sig
       start : Ptime.t;
       finish : Ptime.t;
       result : Builder.execution_result;
-      main_binary : id option;
-      user_id : id;
-      job_id : id;
+      main_binary : [`build_artifact] id option;
+      user_id : [`user] id;
+      job_id : [`job] id;
     }
   end
 
@@ -147,31 +149,31 @@ sig
     (unit, unit, [< `Many | `One | `Zero > `Zero ]) Caqti_request.t
 
   val get_opt :
-    (id, t, [< `Many | `One | `Zero > `One `Zero ]) Caqti_request.t
+    ([`build] id, t, [< `Many | `One | `Zero > `One `Zero ]) Caqti_request.t
   val get_by_uuid :
-    (Uuidm.t, id * t, [< `Many | `One | `Zero > `One `Zero ])
+    (Uuidm.t, [`build] id * t, [< `Many | `One | `Zero > `One `Zero ])
       Caqti_request.t
   val get_all :
-    (id, id * t, [ `Many | `One | `Zero ]) Caqti_request.t
+    ([`job] id, [`build] id * t, [ `Many | `One | `Zero ]) Caqti_request.t
   val get_all_meta :
-    (id, id * Meta.t * file option, [ `Many | `One | `Zero ]) Caqti_request.t
+    ([`job] id, [`build] id * Meta.t * file option, [ `Many | `One | `Zero ]) Caqti_request.t
   val get_latest :
-    (id, id * Meta.t * file option, [< `Many | `One | `Zero > `One `Zero ])
+    ([`job] id, [`build] id * Meta.t * file option, [< `Many | `One | `Zero > `One `Zero ])
       Caqti_request.t
   val get_latest_uuid :
-    (id, id * Uuidm.t, [< `Many | `One | `Zero > `One `Zero ])
+    ([`job] id, [`build] id * Uuidm.t, [< `Many | `One | `Zero > `One `Zero ])
       Caqti_request.t
   val get_latest_successful_uuid :
-    (id, Uuidm.t, [< `Many | `One | `Zero > `One `Zero ])
+    ([`job] id, Uuidm.t, [< `Many | `One | `Zero > `One `Zero ])
       Caqti_request.t
   val get_previous_successful :
-    (id, id * Meta.t, [< `Many | `One | `Zero > `One `Zero ])
+    ([`build] id, [`build] id * Meta.t, [< `Many | `One | `Zero > `One `Zero ])
       Caqti_request.t
   val add : (t, unit, [< `Many | `One | `Zero > `Zero ]) Caqti_request.t
   val get_by_hash :
     (Cstruct.t, string * t, [< `Many | `One | `Zero > `One `Zero]) Caqti_request.t
-  val set_main_binary : (id * id, unit, [< `Many | `One | `Zero > `Zero ]) Caqti_request.t
-  val remove : (id, unit, [< `Many | `One | `Zero > `Zero]) Caqti_request.t
+  val set_main_binary : ([`build] id * [`build_artifact] id, unit, [< `Many | `One | `Zero > `Zero ]) Caqti_request.t
+  val remove : ([`build] id, unit, [< `Many | `One | `Zero > `Zero]) Caqti_request.t
 end
 
 module User : sig
@@ -180,7 +182,7 @@ module User : sig
   val rollback :
     (unit, unit, [< `Many | `One | `Zero > `Zero ]) Caqti_request.t
   val get_user :
-    (string, id * Builder_web_auth.scrypt Builder_web_auth.user_info,
+    (string, [`user] id * Builder_web_auth.scrypt Builder_web_auth.user_info,
      [< `Many | `One | `Zero > `One `Zero ])
     Caqti_request.t
   val get_all :
@@ -188,7 +190,7 @@ module User : sig
   val add :
     (Builder_web_auth.scrypt Builder_web_auth.user_info, unit, [< `Many | `One | `Zero > `Zero ])
     Caqti_request.t
-  val remove : (id, unit, [< `Many | `One | `Zero > `Zero ]) Caqti_request.t
+  val remove : ([`user] id, unit, [< `Many | `One | `Zero > `Zero ]) Caqti_request.t
   val remove_user :
     (string, unit, [< `Many | `One | `Zero > `Zero ]) Caqti_request.t
   val update_user :
@@ -202,11 +204,11 @@ module Access_list : sig
   val rollback :
     (unit, unit, [< `Many | `One | `Zero > `Zero ]) Caqti_request.t
   val get :
-    (id * id, id, [< `Many | `One | `Zero > `One ]) Caqti_request.t
+    ([`user] id * [`job] id, [`access_list] id, [< `Many | `One | `Zero > `One ]) Caqti_request.t
   val add :
-    (id * id, unit, [< `Many | `One | `Zero > `Zero ]) Caqti_request.t
+    ([`user] id * [`job] id, unit, [< `Many | `One | `Zero > `Zero ]) Caqti_request.t
   val remove :
-    (id * id, unit, [< `Many | `One | `Zero > `Zero ]) Caqti_request.t
+    ([`user] id * [`job] id, unit, [< `Many | `One | `Zero > `Zero ]) Caqti_request.t
   val remove_all_by_username :
     (string, unit, [< `Many | `One | `Zero > `Zero ]) Caqti_request.t
 end
diff --git a/db/representation.ml b/db/representation.ml
index dc59122..39cdd6f 100644
--- a/db/representation.ml
+++ b/db/representation.ml
@@ -20,8 +20,11 @@ module Asn = struct
   let console_of_cs, console_to_cs = projections_of console
 end
 
-type id = int64
-let id = Caqti_type.int64
+type untyped_id = int64
+let untyped_id = Caqti_type.int64
+type 'a id = untyped_id
+let id (_ : 'a) : 'a id Caqti_type.t = untyped_id
+let any_id : 'a id Caqti_type.t = untyped_id
 
 type file = {
   filepath : Fpath.t;
@@ -124,3 +127,10 @@ let user_info =
                       scrypt_r; scrypt_p });
          restricted; }  in
   Caqti_type.custom ~encode ~decode rep
+
+(* this doesn't really belong in this module, but we need access to the type of [id] *)
+let last_insert_rowid =
+  Caqti_request.find
+    Caqti_type.unit
+    any_id
+    "SELECT last_insert_rowid()"
diff --git a/lib/model.mli b/lib/model.mli
index 735ed7c..13d8adc 100644
--- a/lib/model.mli
+++ b/lib/model.mli
@@ -15,13 +15,13 @@ val build_artifact : Uuidm.t -> Fpath.t -> Caqti_lwt.connection ->
 val build_artifact_data : Fpath.t -> Builder_db.file ->
   (string, [> error ]) result Lwt.t
 
-val build_artifacts : Builder_db.id -> Caqti_lwt.connection ->
+val build_artifacts : [`build] Builder_db.id -> Caqti_lwt.connection ->
   (Builder_db.file list, [> Caqti_error.call_or_retrieve ]) result Lwt.t
 
 val build : Uuidm.t -> Caqti_lwt.connection ->
-  (Builder_db.id * Builder_db.Build.t, [> error ]) result Lwt.t
+  ([`build] Builder_db.id * Builder_db.Build.t, [> error ]) result Lwt.t
 
-val build_meta : Builder_db.id -> Caqti_lwt.connection ->
+val build_meta : [`job] Builder_db.id -> Caqti_lwt.connection ->
   ((Builder_db.Build.Meta.t * Builder_db.file option) option, [> Caqti_error.call_or_retrieve ]) result Lwt.t
 
 val build_hash : Cstruct.t -> Caqti_lwt.connection ->
@@ -30,16 +30,16 @@ val build_hash : Cstruct.t -> Caqti_lwt.connection ->
 val build_exists : Uuidm.t -> Caqti_lwt.connection ->
   (bool, [> Caqti_error.call_or_retrieve ]) result Lwt.t
 
-val latest_build_uuid : Builder_db.id -> Caqti_lwt.connection ->
+val latest_build_uuid : [`job] Builder_db.id -> Caqti_lwt.connection ->
   (Uuidm.t, [> error ]) result Lwt.t
 
-val latest_successful_build_uuid : Builder_db.id -> Caqti_lwt.connection ->
+val latest_successful_build_uuid : [`job] Builder_db.id -> Caqti_lwt.connection ->
   (Uuidm.t option, [> Caqti_error.call_or_retrieve ]) result Lwt.t
 
-val previous_successful_build : Builder_db.id -> Caqti_lwt.connection ->
+val previous_successful_build : [`build] Builder_db.id -> Caqti_lwt.connection ->
   (Builder_db.Build.Meta.t option, [> Caqti_error.call_or_retrieve ]) result Lwt.t
 
-val main_binary : Builder_db.id -> Fpath.t option -> Caqti_lwt.connection ->
+val main_binary : [`build] Builder_db.id -> Fpath.t option -> Caqti_lwt.connection ->
   (Builder_db.file option, [> Caqti_error.call_or_retrieve ]) result Lwt.t
 
 val readme : string -> Caqti_lwt.connection ->
@@ -49,25 +49,25 @@ val job_and_readme : string -> Caqti_lwt.connection ->
   (string option * (Builder_db.Build.Meta.t * Builder_db.file option) list, [> error ]) result Lwt.t
 
 val job_id : string -> Caqti_lwt.connection ->
-  (Builder_db.id option, [> Caqti_error.call_or_retrieve ]) result Lwt.t
+  ([`job] Builder_db.id option, [> Caqti_error.call_or_retrieve ]) result Lwt.t
 
 val jobs : Caqti_lwt.connection ->
-  ((Builder_db.id * string) list, [> Caqti_error.call_or_retrieve ]) result Lwt.t
+  (([`job] Builder_db.id * string) list, [> Caqti_error.call_or_retrieve ]) result Lwt.t
 
 val jobs_with_section_synopsis : Caqti_lwt.connection ->
-  ((Builder_db.id * string * string option * string option) list, [> Caqti_error.call_or_retrieve ]) result Lwt.t
+  (([`job] Builder_db.id * string * string option * string option) list, [> Caqti_error.call_or_retrieve ]) result Lwt.t
 
-val job_name : Builder_db.id -> Caqti_lwt.connection ->
+val job_name : [`job] Builder_db.id -> Caqti_lwt.connection ->
   (string, [> Caqti_error.call_or_retrieve ]) result Lwt.t
 
 val user : string -> Caqti_lwt.connection ->
-  ((Builder_db.id * Builder_web_auth.scrypt Builder_web_auth.user_info) option, [> Caqti_error.call_or_retrieve ]) result Lwt.t
+  (([`user] Builder_db.id * Builder_web_auth.scrypt Builder_web_auth.user_info) option, [> Caqti_error.call_or_retrieve ]) result Lwt.t
 
-val authorized : Builder_db.id -> string -> Caqti_lwt.connection -> (unit, [> Caqti_error.call_or_retrieve | `Msg of string ]) result Lwt.t
+val authorized : [`user] Builder_db.id -> string -> Caqti_lwt.connection -> (unit, [> Caqti_error.call_or_retrieve | `Msg of string ]) result Lwt.t
 
 val add_build :
   Fpath.t ->
-  Builder_db.id ->
+  [`user] Builder_db.id ->
   (Builder.script_job * Uuidm.t * (int * string) list * Ptime.t * Ptime.t *
    Builder.execution_result * (Fpath.t * string) list) ->
   Caqti_lwt.connection ->